VITAMIN D & NUTRITION » do you need supplements?
Let's talk Vitamin D
Is it something only vegans need?
What about the general population?
Do we get enough from the sun? Do we need supplements?
Let's answer these questions and more...
Vitamin D in Brief Insufficient vitamin D is associated with increased risk for depression, cardiovascular disease, respiratory tract infections, type 2 diabetes, and increased risk of birthing complications. Needless to say, vitamin D has many important biological roles.
One other vital function this vitamin plays is in bone health: vitamin D helps to increase the absorption of calcium in the gut, helps to regulate calcium levels in the blood and decreases calcium loss in the urine if levels of this mineral are low. For more information on calcium and what you need, check out this PUL article.
Vitamin D Recommendations
International Units (IU), as well as micrograms (mcg),as well as are both units of measure used when discussing amounts of Vitamin D. To convert IU to mcg, simply divide by 40.
Adults < 71 years: 600 IU (15 mcg) daily
Adults > 71 years: 800 IU (20 mcg) daily
For optimal health, some experts recommend 1000 to 2000 IU (25 - 50 mcg) of vitamin D2 or D3 daily
Tolerable Upper Intake (maximum): stay below 4000 IU/day (100mcg/day) from combined food + supplement unless under medical supervision
Vitamin D Sources
There are three common sources: sun, food and supplements. Let's explore each of these in more detail.
1. Sunshine: our bodies can use the sun's rays (ultraviolet light, in particular) to convert inactive vitamin D into its active form when the sun comes in contact with our bare skin. Amazing stuff. But there are some things to consider:
Location on planet earth. In some places closer to the equator 10-15 minutes of whole-body exposure in the mid-day summer sun is equivalent to taking 15,000 IU (375 mcg) Vitamin D3 orally. In countries like Canada 30 minutes or less is needed to make 1000 IU (25 mcg) Vitamin D3 in summer months; in the spring about 60 minutes is needed. In the fall and winter months, the sun's rays are inadequate to meet the needs of most. Of course, depending on where you live the intensity of the sun can differ, especially at different months of the year.
Skin exposure to the sun. Of course, the skin needs to be bare for the UV rays to penetrate the skin. This means no clothes and no sunscreen, otherwise, insufficient vitamin D is produced by the body.
Skin colour. Darker pigmented skin is less efficient at converting vitamin D to the active form; therefore longer exposure to sun is required than for a person with more fair skin.
Age. Unfortunately, the efficiency of vitamin D conversion decreases with age.
2. Food Sources: although animal products such as milk, egg yolks and certain types of fish offer vitamin D, they do not offer it in amounts that are sufficient to meet recommended needs on a daily basis. This is also true for plant-based sources such as fortified non-dairy beverages which offer only about 100 IU (2.5 mcg) vitamin D per 250 mL serving. Therefore, vegan and non-vegan food sources are insufficient to meet our vitamin D needs.
3. Supplements: in a city like Vancouver, Canada, the sun's rays are only strong enough for our bodies to make vitamin D between April and September; during the other months, supplements are needed. Depending on where you live, supplements may not be needed if you are exposed to an adequate amount of sun for 15-60 minutes a day, with some skin exposed. See a dietitian or doctor if you need more information.
Vitamin D Supplements: Types
There are two kinds:
Vitamin D2 (also known as ergocalciferol)
This source is vegan and is made when yeast is exposed to UV light
Vitamin D3 (also known as cholecalciferol)
This source is generally not vegan and is made when sheep's wool is exposed to UV light.
Vegan sources made from lichen, a plant, are now available but can be difficult to find and are rather expensive.
Important notes regarding supplementation
Effectiveness: research comparing the two types of vitamins shows that vitamin D2 tends to be less potent, meaning larger doses may be needed to achieve the same effect. It is generally safe to supplement with 1000 to 2000 IU (25 - 50 mcg) of vitamin D2, although you should speak with your physician if you have any concerns.
Obese individuals: research indicates obese individuals are at greater risk for insufficient vitamin D. This is likely due to the extra adipose tissue (fat cells) that store the vitamin D, although many possible mechanisms for why this deficiency is observed have been reported.
Multivitamins: remember these can also contain vitamin D - consider this when calculating your total intake.
Taken with food: studies indicate vitamin D does not need to be taken with food to be absorbed, despite being a fat-soluble vitamin. It can be taken either with or without food.
Supplement type: there is no difference in absorption of vitamin D supplements if they are liquid, chewable, or tablets.
Side effects: taking too much vitamin D in the form of supplements can cause too much calcium to be absorbed. Over several weeks or months this can cause the calcium to deposit in the arteries, thereby hardening them. This may increase the risk of cardiovascular events. Too much sun exposure, however, has not been shown to have this effect.